The magnetic surfaces of the disks used for data storage must be extremely smooth with peak-to-valley roughness of some thin film disks being less than 100 Angstroms. The design of most disk drives allows the sliders to rest on the disk surface when the disk is not spinning. If the sliders were allowed to rest on a very smooth surface, the result would be unacceptably high stiction forces between the disk surface and the sliders. For high areal density recording, the slider must fly in close proximity to the disk surface which requires that the surface be very smooth. The trend is, therefore, toward lower flying heights and smoother disks. To reduce the stiction forces between sliders and smooth disks, a band on the disk surface may be deliberately roughened by laser texturing to form a contact start/stop (CSS) region. While the roughened CSS region decreases stiction, it has the undesirable effect of increasing the energy dissipation during disk spin up and spin down. Energy dissipation is directly related to wear.
Various techniques for creating CSS regions have been proposed. Published unexamined Japanese patent application (PUPA) 4-362517 describes the use of a groove in the disk surface adjacent to the CSS in which one rail of the slider rests when the disk is not operating. Alternatively it describes the use of a round protrusion on which the slider rail can rest. Each of these techniques results in the slider being tilted from a parallel position on the disk surface. PUPA 4-38716 suggests cutting spiral grooves into the landing zone under the slider rails. Anonymous Research Disclosure 29563 published in 1988 suggests that "[s]liders with multiple rails may need textured landing zones for one or more of the rails."
Laser texturing of a CSS is described by Ranjan, et al., in J. Appl. Phys. April 1991 p. 5746ff. The average surface roughness (Ra) was varied by altering the beam current. U.S. Pat. No. 5,528,922 describes the use of increased number of laser pulses to increase the height of a peripheral ridge in crater shaped bumps. U.S. Pat. No. 5,062,021 describes the use of laser created bumps to form a CSS region, controlling depth and height of the bumps by varying the laser power and pulse duration, and altering the shape of the bumps by varying the laser beam inclination relative to the disk surface.